Recently, in other topic, some people have been discussing about downsizing their files when uploading to those agencies who works with subscription plans. I confess I have never thought about it, and I'm interested, because is frustating when you have many subscribtion sales in wich you gain $0.20-0.40 depending on the site, for files at maximum size.

Subscription sites I contribute to are:
Fotolia - min 4Mp (2400*1600)
Dreamstime - min 3Mp (2000*1500)
Canstockphotos - don't know minimum
Depositphotos - min 4Mp (2400*1600)
123RF - min 6Mp (2900*2175 aprox)
Panthermedia - doesn't matter since you have the chance to disable subscription sales.
Crestock - don't know minimum
Pixmac - min 3Mp (3000*1500)

I'm temptated to only upload files to those sites at the minimum size, but...
For example, in Dremstime, I have had 42 sales until now, many of them subscripted, others no. Of those 42, 6 (one of seven) I have sold no-subscripted and at a size large or maximum. That kind of sales produces a satisfaction, is when I see my little gains grown. And I would have lose part of this money if I have uploaded the files at the minimum size required. I even think that many of the subscription-frustrating sales could not be existed if I haven't had the maximum size of the file, and buyer could have chosen another photographer's file (and little by little, they are a strong percentage of gains).

I would like to know what do you think about this question. Someone in the other post says he upload in subscription sites at a size of 5Mp, when his camera has 17 or 18, don't remenber, and argues that downsizing also increases quality of files (in many cases it's truth that the file is better this way).

What do you do? What do you think about?